1. Field of the Invention
This invention relates to dental instrumentation devices, and more particularly, to a mandibular electromyograph for measuring and displaying various comparisons of timing and amplitude characteristics of the masticatory muscles.
2. Description of the Prior Art
Electromyographs utilize conventional electrodes placed on the surface of the skin to pick up electric potentials generated by contraction of the muscles beneath the skin. Electromyographs have long been used in the medical and dental fields for a variety of purposes, including the examination of masticatory muscles for pathological conditions. The masticatory muscles are muscles of the human body which produce mandibular movement associated with chewing.
Although mandibular electromyographs have been previously used, their use is limited by the difficulty of interpreting the information thereby obtained. In the conventional mandibular electromyograph, the electric potentials from the electrodes are amplified, filtered, and then usually applied directly to the X axis of an oscilloscope or strip chart recorder. The characteristics of a single masticatory muscle are examined by measuring the spacing of various portions of the electrode signal on the oscilloscope screen or strip chart. The accuracy of this technique is inherently limited by the resolution of rulers or scales printed on the strip chart. Furthermore, it requires a great deal of concentration by the practitioner administering the test. The characteristics of masticatory muscle contractions can only be compared to the contractions of other masticatory muscles with a great deal of difficulty. Such comparisons are traditionally made by simultaneously displaying two, four, or more channels, each containing an electrode output, on the oscilloscope or strip chart at the same time. Use of this technique is even more difficult with an oscilloscope since it is extremely difficult to simultaneously examine multiple traces on the oscilloscope screen. This technique is used with strip chart recorders by manually drawing transverse lines across the strip chart and comparing the recording for each channel with the line. The line drawing and comparing process is, of course, slow and tedious.
As a result of the foregoing disadvantages, mandibular electromyographs have not achieved widespread acceptance for clinical use, but instead, have remained a laboratory tool or a device used by relatively few practitioners.